1. Field of the Invention
The present invention relates to a voice processing apparatus, and more particularly to a voice processing apparatus capable of varying the speech speed by skipping or repeating the feature parameters used in the voice synthesis.
2. Related Background Art
Voice signals are almost constant within a certain period. This fact is utilized in the conventional voice synthesizing process, in which a voice signal is analyzed in each predetermined period and is represented by a set of feature parameters in each period, and, at the voice synthesis, the voice signal is reproduced in each period by the feature parameters stored in advance. This process is practical since the synthesizing operation is very simple and the deterioration in voice quality is limited. In this process, a set of feature parameters corresponds to the voice of a predetermined period. Consequently the duration of the synthesized voice can be changed by suitably skipping or repeating the sets of feature parameters. It has conventionally been tried to vary the speech speed by this method. However plosive consonants (k, t, p, b, d, g, r, etc.) are represented by only one or two sets of parameters at maximum since these consonants have a short duration. Consequently, in the conventional process, the clarity of speech is significantly deteriorated if the skipped or repeated set of parameters happens to correspond to a plosive consonant.